2.O. Can I reenter if I left while on OPT? If your OPT has been approved and you depart before you get a job, your OPT ends and you cannot reenter unless you have a written job offer. If you have a job, you may travel and reenter to resume work at the same job or you have a written offer for another job. http://www.ice.gov/sevis/travel/faq_f2.htm#_Toc81222042
If you leave the country when your H1-B is in process, your I-94 in your application will not be valid, it would be a messy situation. Consult with your school or company.